It may not be the best smelling type of resource and you might not even want to know where it comes from, but you still need to.
Fertilizer in Ark is made up of creature (and even human) feces which often is done by the process of combining feces and Thatch.
When you start planting seeds in Crop Plots, you will need a Fertilizer to allow your plants to grow (crops do not grow and will die without Fertilizer) more efficiently in Ark.
Also read our other guides of ARK:
How To Make Fertilizer?
Fertilizer does not require any level to be made, but you will need to use either a Compost Bin or a Dung Beetle to create it.
Fertilizer is created using 3 Feces and Thatch, which creates 1 fertilizer, but for a Dung Beetle, you just place the feces in its inventory without the need for Thatch.
Over time, the Compost Bin will slowly create Fertilizer, using up a certain amount of feces depending on how big it is and the Thatch.
For Dung Beetles, placing feces in their inventory and setting them to wander will cause them to produce not only Fertilizer but Oil as well.
When you are planting, your crops will require Fertilizer, which is drained over time and can be considered the health of your plant.
This is different however with the Plant X Species plant, which uses the Fertilizer as ammo when attacking enemies.
You will need to supply your plants with a lot of Fertilizer (feces if you don’t have enough) so that they stay alive.
If you attempt to grow your crops, you must have a way of obtaining Fertilizer, which is to have multiple Compost Bins, Dung Beetles, or even both.
The more sources for Fertilizer you have, the more sufficient and less tedious farming your crops will be once they grow.
You can still use feces as a substitute for Fertilizer but it will never provide the same value that Fertilizer does for plants.
Bases with Plant X Species as a line of defense will need a good amount of Fertilizer for each of the plants that defend a base.